1. Field of the Invention
The present invention relates to a method and apparatus for securing a quality of service of packet data service provided in a communication system.
2. Discussion of the Related Art
The universal mobile telecommunications system (UMTS) is a third-generation mobile communications system evolving from the global system for mobile communications system, which is the European standard. The UMTS is aimed at providing enhanced mobile communications services based on the GSM core network and wideband code-division multiple-access technologies.
A conventional UMTS network structure 1 is illustrated in FIG. 1. One mobile terminal 2, or user equipment (UE), is connected to a core network 4 through a UMTS terrestrial radio access network (UTRAN) 6. The UTRAN 6 configures, maintains, and manages a radio access bearer for communications between the UE 2 and core network 4 to meet end-to-end quality-of-service requirements.
The UTRAN 6 includes a plurality of radio network subsystems 8, each of which comprises one radio network controller (RNC) 10 for a plurality of base stations 12, or “Node Bs.” The RNC 10 connected to a given base station 12 is the controlling RNC for allocating and managing the common resources provided for any number of UEs 2 operating in one cell. The controlling RNC 10 controls traffic load, cell congestion, and the acceptance of new radio links. Each Node B 12 may receive an uplink signal from a UE 2 and may transmit downlink signals to the UE. Each Node B 12 serves as an access point enabling a UE 2 to connect to the UTRAN 6, while an RNC 10 serves as an access point for connecting the corresponding Node Bs to the core network 4.
Services provided to a specific UE 2 include circuit-switched services, for example voice, and packet-switched services, for example web browsing. In a communication system supporting circuit-switched services, the RNCs 10 are connected to a mobile switching center (MSC) 12 of the core network 4, and the MSC is connected to the gateway mobile switching center (GMSC) 14 managing the access of a voice call requested from or to an external network. Packet-switched services are provided by a serving GPRS support node (SGSN) 16 and a gateway GPRS support node (GGSN) 18 of the core network 4. The GGSN 18 manages a connection to Internet or other external packet-switched networks and the SGSN 16 supports packet communications toward the RNCs 10. An example of a packet-switched service is a multimedia broadcast/multicast service (MBMS), which provides MBMS data from the core network 4 to a UE 2.
The air interface between a UE 2 and the UTRAN 6 includes a radio resource control (RRC) layer (not shown) for the establishment, reconfiguration, and release of radio bearers. A radio bearer is a service providing data transfer between a UE 2 and an RNC 10 of the UTRAN 6 and is established as a point-to-point radio bearer or point-to-multipoint radio bearer according to a radio resource management state, which considers the number of UEs in a cell to be provided with a specific MBMS.
A UE 2 is said to be in the RRC-connected mode when the RRC layer of a UE and the RRC layer of a corresponding RNC 10 are connected, thus providing for a bi-directional transfer of RRC messages. If there is no RRC connection, the UE 2 is said to be in the RRC-idle mode.
When a point-to-multipoint radio bearer is established for a specific service to be provided in a specific cell, the UTRAN 6 directs some of the UEs 2 of the cell to enter the RRC-connected mode and directs the remainder of the UEs to remain in the RRC-idle mode. For example, after having received RRC-connection requests from the UEs 2 intending to receive a specific service via an uplink common control channel, the UTRAN 6 transmits an RRC-connection setup message or an RRC-connection rejection message to the UEs according to the radio resource management state.
UEs 2 receiving the RRC-connection setup message are controlled to receive the corresponding service in the RRC-connected mode and UEs receiving the RRC-connection rejection message are controlled to receive the corresponding service in the RRC-idle mode. A UE 2 having completed an RRC connection to the UTRAN 6 can send a variety of messages according to the control of the UTRAN.
FIG. 2 illustrates a conventional method 50 carried out between the UTRAN 6 and a UE 2 in which an RRC connection is established. The UTRAN 6 receives an RRC connection request (S51) from a corresponding UE 2 requesting an RRC connection for a specific service. In response, the UTRAN 6 transmits an RRC connection setup message (S52) to the UE 2.
The RRC connection is established, thereby setting up a transmission and reception environment per the RRC connection setup message received from the UTRAN 6 and the UE 2 transmits an RRC connection setup complete message (S53) to the UTRAN 6. Thereafter, the UE 2 and UTRAN 6 carry out a predetermined procedure permitting the UE, which is now in the RRC-connected mode, to receive the data of the MBMS (S54).
To more effectively manage the established radio bearer and to secure a minimum quality of service (QoS) for a specific MBMS, the UTRAN 6 transmits a measurement request message requesting the UE 2 to measure the quality of data received from the UTRAN (S55). After measuring the quality of the received data, the UE 2 reports the results to the UTRAN 6 (S56).
The report from the UE 2 enables the UTRAN 6 to adjust variables, such as coding and power levels, allocated for the service. For example, the UTRAN 6 may allocate more transmission power for the MBMS if the report from UE 2 indicates an excessive error rate in the MBMS data or may reduce the power if the report from UE indicates that the signal strength is too high.
The measurement request message informs a UE 2 of how often, or at what interval, to measure a certain parameter to determine the current condition of data transmission and when to report the measurement results to the UTRAN 6. If conditions for reporting the measurement results are met, the UE 2 uses a dedicated control channel to transmit a measurement report (S56) to the UTRAN. The measurement report includes measurement results for a corresponding service.
Any UE 2 having established a point-to-point radio bearer and receiving the corresponding service can provide a measurement report to the UTRAN 6. However, if a point-to-multipoint radio bearer is established, UEs 2 are selectively RRC-connected based on the availability of a dedicated control channel. Therefore, a UE 2 can provide the UTRAN 6 with feedback information, for example QoS information based on the received data packet, only if an RRC connection to the UTRAN 6 is established.
When an MBMS is provided within a cell via a point-to-multipoint radio bearer, a UE 2 receiving service data in the RRC-idle mode has no RRC connection and, therefore, may not be instructed to perform measurements of the quality of received data or provide a corresponding measurement report to the UTRAN 6. Therefore, an RRC-idle UE 2 may be provided with the service from the UTRAN 6, but is unable to inform the UTRAN if the quality of the service is poor and may be unable to secure a minimum quality of service.
Therefore, there is a need for a method and apparatus for enabling a mobile terminal receiving a service in the RRC-idle mode to provide information regarding the quality of the service received to the network. The present invention addresses these and other needs.